The present invention relates to vacuum processing apparatus for semiconductor wafers and other objects of processing.
Conventionally, there have been known etching apparatus, ashing apparatus, ion injection apparatus, spatter apparatus, pressure reduction CVD apparatus and other types of vacuum processing apparatus which house semiconductor wafers or some other objects of processing inside a vacuum processing chamber and implement a required processing to the object of processing when there is an atmosphere of reduced pressure.
In such vacuum processing apparatus, once the inside of the vacuum-- processing chamber is returned to normal pressure, it is necessary to-have an extremely long time until the inside of the vacuum processing chamber is set to the required degree of vacuum and there is the status where the next processing can be started. Because of this, there are many instances where a load-lock chamber or pre-vacuum chamber having a comparatively small volume when compared to the vacuum processing chamber is provided adjacent to the vacuum processing chamber, so that simply returning this load-lock chamber to normal pressure enables the semiconductor wafers of other objects of processing to be carried in and out of the vacuum pressure chamber via this load-lock chamber.
FIG. 10 shows an outline configuration of an etching apparatus which is one example of such a conventional type of vacuum pressure apparatus. Inside the vacuum processing chamber 50 which is configured so that the inside is airtight, the upper portion is provided a lower portion electrode 52 which is also a wafer mounting platform configured so as to enable the mounting of a semiconductor wafer 51. This lower portion electrode 52 is driven by a drive mechanism 53 and is provided with a wafer clamp mechanism 54 which presses against and holds the peripheral edge portion of the semiconductor wafer 51. In addition, internal to the lower portion electrode 52 are provided cooling mechanisms 55a.about.55c for circulating helium gas or some other coolant gas for cooling the semiconductor wafer 51.
In addition, to the top of the lower portion electrode 52 is provided an upper portion electrode 56 formed in the shape of a cylinder. To the lower surface of this upper portion electrode 56 are provided many holes 56a and the required etching gas supplied from the processing gas supply pipe 57 flows from these holes 56a and is supplied in the direction of the processing surface of the semiconductor wafer 51 mounted on the lower portion electrode 52. Between the upper portion electrode 56 and the lower portion electrode 52 can be impressed a high-frequency voltage from a high-frequency power source (not shown).
Furthermore, a vacuum exhaust pipe 58 connected to a vacuum exhaust pump is connected to the vacuum processing chamber 50 in a configuration whereby the inside of the vacuum processing chamber 50 can have vacuum suction to a required degree of vacuum. In addition, to the side portion of the vacuum processing chamber 50 is provided a carrying-in and -out opening 59 for carrying-in and -out the semiconductor wafer 51, and this carrying-in and -out opening 59 is provided with a gate valve 60 airtightly sealing the carrying-in and -out opening 59. Furthermore, to the outer side of the gate valve 60 is provided a load-lock chamber 61. A gas introduction pipe 63 for the supply of nitrogen gas or some other required cleaned gas and a vacuum exhaust pipe 62 connected to the vacuum exhaust pump (not shown) are both connected to this load-lock chamber 61 in a configuration where the inside of the load-lock chamber 61 is set to a required degree of vacuum and can be returned to an atmospheric pressure for opening. In addition, the inside of the load-lock chamber 61 is provided with a conveyor arm 64 for conveying the semiconductor wafer 51, and a side portion of the load-lock chamber 61 is provided with a carrying-in and -out opening 65 for carrying-in and -out the semiconductor wafer 51. This carrying-in and -out opening 65 is provided with a gate valve 66 for airtightly sealing the carrying-in and -out opening 65 and here is for example arranged an auto-loader 67 having a wafer carriers (not shown) and the like arranged to it.
In such a vacuum processing apparatus, the configuration is such that the load-lock chamber 61 is first set to a large pressure, the gate valve 66 is opened and the contraction and extension of the conveyor arm 64 carries the semiconductor wafer 51 from the autoloader 67 into the load-lock chamber 61. After this, the gate valve 66 is then opened, and the semiconductor wafer 51 is mounted on the lower portion electrode 52 of the vacuum processing chamber 50. By carrying the semiconductor wafer 51 into the gate valve 60 via the load-lock chamber 61, it is possible to carry in the semiconductor wafer 51 without having to return the inside of the vacuum processing chamber 50 to a large pressure. Moreover, the carrying out of the semiconductor wafer 51 is performed using a procedure the reverse of that described above.
In addition, inside the vacuum processing chamber 50, the peripheral edge portion of the semiconductor wafer 51 is pressed against and held by the wafer clamp mechanism 54, and while the semiconductor wafer 51 is cooled by the cooling mechanisms 55a.about.55c, etching gas is supplied from the lower surface of the upper portion electrode 56 and is activated by a high-frequency voltage impressed between the lower portion electrode 52 and the upper portion electrode 56 to implement etching processing to the semiconductor wafer 51. Moreover, at this time, vacuum suction is implemented by the vacuum exhaust pipe 58 and the inside of the vacuum processing chamber 50 is held at a required degree of vacuum.
However, with such a vacuum processing apparatus, the inside of the load-lock chamber 61 contains many reaction products generated inside the vacuum processing chamber 50, and dust and other particles generated from mechanical drive portions such as the gate valve 60, 66 and the processing object conveyor mechanism and the like. When vacuum suction of the inside of the load-lock chamber 61 is performed or when nitrogen or some other gas is introduced into the load-lock chamber 61 to return it to normal pressure for opening, these particles (with a size of about 0.3.about.0.5 .mu.m) rise with the sudden stream of air upon opening and cause a problem in that they adhere to the semiconductor wafer 51 and the like. This problem is a large problem in that it causes an increased number of defective products in semiconductor device manufacturing processes using semiconductor wafer 51 and the like, and a consequent drop in the yield.
Because of this, with a conventional vacuum processing apparatus, a slow exhaust method in which air is slowly exhausted from the load-lock chamber 61 and a slow vent method whereby air is slowly reintroduced to the load-lock chamber 61 are used so that this rising of particles inside the load-lock chamber 61 is controlled.
However, with such a conventional vacuum processing apparatus, controlling the rise of particles inside the load-lock chamber 61 by the slow-exhaust or the slow-vent method involves an increase in the time for vacuum exhaust and for opening to the atmosphere and this therefore involves the problem of reduced throughput. Furthermore, even if slow exhaust and slow vent are performed, it is difficult to completely prevent the rise of particles, as some particles still adhere to the semiconductor wafer and cause faults, and the same problem of reduction of the yield.